1. Field of the Invention
This invention relates to a method for settling suspended finely divided solid, particularly inorganic solid, particles from a hydrocarbon. This invention particularly relates to a method for settling such solids from a hydrocarbon using a additive.
2. Background of the Invention
Solid settlement or separation or removal may be very important for naturally occurring formation fluids such as crude oil or crude oil from tar sand, oil shale or other naturally occurring bitumen, bottoms from various oil refining processes, resid and numerous streams from chemical or polymer plants. All of these streams are known to exist as slurries and contain different types and varying amounts of suspended finely divided solid particles. These finely divided solid particles could be inorganic materials such as sand, clay, dirt or catalyst, insoluble organic compounds, organometallic compounds, or mixtures of such insoluble organic, inorganic and organometallic compounds. These solid particles could exist in a wide range of sizes and shapes. In general, larger or coarser particles are easier to separate than smaller or finer particles of the same density.
If crude oil, crude oil from tar sand, oil shale or other naturally occurring bitumen, or other formation fluids contain a high concentration of suspended solid particles, it may not be feasible to use or process the feedstock in an existing plant or refinery. The solid particles need to be completely or substantially separated from other products in the slurries as part of a purification step. Typically, the suspended solid particles are first rendered to settle. Then, they are separated and removed. Recovery and production of minerals or metals also may require similar types of settlement and separation of inorganic solid particle products from aqueous slurries.
Many different methods and equipment have been used to settle, separate, remove or recover from a variety of slurry mixtures, as discussed in the foregoing examples, the suspended finely divided solid particles. These methods and equipment include sedimentation, magnetic separation if the particles are magnetic, and/or use of processing equipment such as hydrocyclones and centrifugal separators. In processes where direct physical and/or mechanical separations are not economical, technically feasible, or fast enough, different chemicals may be used to effect, aid, improve and/or accelerate settling of such finely divided solid particles upon standing, storage, centrifugation or other ways. For instance, U.S. Pat. No. 5,481,059 discloses uses of adducts between alkylphenolformaldehyde resin alkoxylate compound and polyacrylic acid to aid solid particle settlement. U.S. Pat. No. 5,476,988 discloses a method of accelerating settlement of finely divided solids from hydrocarbon fluids and slurries by adding certain quaternary fatty ammonium compounds to the slurries.
To be effective, it is generally desirable to use chemical aids, additives and/or polymers that are large, easy to separate and/or capable of forming a settled phase with the finely divided solids suspended in the slurry through various interactions. Such interactions include, but are not limited to, chemical, physical, electrostatic, Van Der Waals, or a combination thereof. It is also desirable to form a settled phase, a sludge or other forms of precipitation between the solids and the additive that are more readily separable from the fluid or liquid phase of the slurry using conventional equipment. Furthermore, it would be advantageous to accelerate the settling of the finely divided solids, especially inorganic solids, to shorten the settling time required to achieve the desired level of residual solids in the fluid/liquid phase. This would help reduce the size of the settling tank or other related equipment and/or increase the throughput of the process. It also would be an advantage if these chemical aids, additives or polymers are (a) readily available or prepared or (b) more effective than those already known or (c) both.